They were going up 10-20% on average per year before ACA.
People are living longer, and have a longer period of old age in which to spend on this. The vast majority of health spending is on the last years of life.
Technology is drastically advancing, but is become more expensive. Privately insured want the best they can afford.
Diabetes. Obesity. Opioids, etc is driving usage up, which means more clinics and more costs.